dhenry:
I tried this circuit a while ago in a breadboard and it is not a working.
That circuit is designed for the pnp to kick in at load current > 700mv/1ohm = 700ma. Anything below that, the voltage regulator is doing the heavy lifting.
If you want the pnp to kick in at a lower current, increase that 1ohm resistor.
I see. What do you suggest?